1. Field of the Invention
This invention relates to a method of guiding industrial trucks having at least one steerable wheel, wherein a direction-controlling signal is transmitted to the industrial truck.
The invention relates also to a system for carrying out a method outlined herein in order to guide industrial trucks having at least one steerable driven wheel and a sensor, which is disposed at the center of the truck and cooperates with a guiding signal line in or on the ground and serves to scan the guiding signal line and is connected to steering means for controlling the deflection of steerable vehicle wheels. The guiding signal line is provided with branch lines for a deflection toward the left or right from a straight course.
2. Description of the Prior Art
Such systems are known in numerous forms, including systems having branch lines. Attention is directed in that connection to German Pat. No. 1,806,750. The system disclosed there has the disadvantage that control means must be associated with each of the guiding wire sections which have been laid in the ground. Owing to branches and junctions it is necessary to provide signal receivers which can selectively be enabled. The signal receivers are disposed in part in the ground at the point of intersection or at the point where a decision is to be taken and will respond to a signal from the vehicle in that a conductor section which was previously deenergized is now reenergized. This will permit of changing control actions. In the known system the first and second line sections at a crossing may be substantially parallel and may be connected by a bistable circuit to a course-defining conductor and may include each a monostable circuit for actuating an associated bistable circuit. This arrangement gives rise to considerable problems.
A system for guiding industrial trucks in accordance with the above explanations is also described in German Pat. No. 1,530,894. In connection with switchless junctions that publication deals specifically with the guidance of a vehicle having a mechanical connecting element, which is preset to a predetermined direction by a program control, which is initiated by detectors when they are disposed before a junction in the longitudinal guide for the stacking truck. That design permits a particularly favorable adaptation of a steering system and the detectors may be responsive to elevations, depressions or selective influences of that kind.
It is also known to provide a control system for a self-contained route system, which is described as a network and includes a plurality of switches or junctions, each of which permits a selection of two directions, and which also includes vehicles which are provided with a destination selector provided with memories and adapted to designate a given destination zone of the route system. The selection of the destination zone is a particularly important feature also in the present application.
The known system also comprises actuating means for selecting a direction in the area covered by the routes. A destination selector is provided with motor-controlling means, particularly for stopping the travel motor. The steering motor may also be controlled for an adjustment of a predetermined deflection. This can easily be achieved if, in the known system, each switch or junction is provided with a certain code for selecting a direction and the vehicle is provided with a receiver in conjunction with a comparator.
That known embodiment is provided at each switch with a transmitter having a predetermined code, which constitutes a constant signal train consisting of a predetermined number of signal steps, which are selectively provided with various signal marks, particularly signal pulses. A destination mark is provided by an additional signal within a signal step in a region in which there are no signal pulses. In that case the vehicle is provided with a comparator, which is provided with the destination code and receives signals, a zone signal train having a number of signal steps is provided for a network and the number of signal steps is at least as large as the number of possible destination zones in that network. That system can be controlled with very high accuracy. The system may be divided into various regions so that the route system is divided into a plurality of interconnected networks, and an additional network signal train comprising signal steps in a number which is at least as large as the number of networks is provided for such networks.
Such a control system provided with a destination code affords the advantage that a vehicle may selectively be provided with a starting code and when the latter has been activated a control will be effected by the destination code.
In a system for guiding industrial trucks, a block post control may be performed in accordance with German Pat. No. 1,806,750. But that would be inconsistent with the principle underlying the present application, in which the parts buried in the ground are set to and maintained in a predetermined state.
If a junction is provided in accordance with the invention and a branch guide wire departs from the normal guide wire, that branch guide wire may be separately energized. That energization is constant and will not be changed in dependence on the passage of the vehicle, which will be controlled by the direction-presetting subassembly for controlling the direction in which the vehicle is to be steered to either follow a branch or to go ahead on the previous course.